1. Field of the Invention
This invention relates to new moldable, radical-polymerizable multicomponent mixtures which are used, for example, as free-flowing or spreadable compositions or as pastes and which subsequently cure under ambient conditions with initiation of the polymerization reaction at room temperature and/or elevated temperatures. In applicational terms, the invention covers almost all fields involving the use of radical-polymerizable or curable compositions, including for example adhesives, sealing compounds, the selective production of plastic moldings, surface-coating with air-curing and, in particular, solventless lacquer systems and the like.
2. Discussion of Related Art
The peroxide- or hydroperoxide-initiated curing of olefinically unsaturated systems requires selected starters or activator systems particularly when the reaction is to be initiated at low temperatures, for example at room temperature or only slightly elevated temperatures. For example, it is known that a corresponding activating function is performed by selected tertiary amine compounds with partly aromatic substitution at the nitrogen atom. Known activators for the initiation of polymerization reactions, for example with dibenzoyl peroxide, are in particular dimethyl aniline and dimethyl p-toluidine.
A totally different known class of activators for the oxidative polymerization initiation of certain unsaturated systems, namely drying oils, are metal compounds--at least partly soluble in the system--of metals which can occur in several valency stages and which accelerate the starting reaction through intermediate shifts in valency on interaction with other components of this system. These metal compounds, which are sufficiently soluble in organic solvents and/or in binders, have been known for some time as so-called drying agents for the air drying of paints, varnishes and the like based on unsaturated oils. Sufficiently oil-soluble compounds of transition metals which are capable of occurring in several valency stages are particularly suitable for this purpose. The individual components differ in their ability to accelerate curing. Compounds of cobalt and/or manganese are mainly used for this purpose, although iron also accelerates curing. Comparable compounds of other metals which are also capable of occurring in several valency stages may be used in addition to and, in particular, in combination with these highly effective metal components. A detailed description of such systems can be found, for example, in Ullmann, "Encyklopadie der technischen Chemie", 4th Edition, Vol. 23 (1983), 421 to 424.
U.S. Pat. Nos. 4,010,152 and 4,063,012 describe the (co)polymerization of ethylenically unsaturated monomers, such as vinyl chloride, with selected aliphatic .alpha.-(hydroperoxy)-azo compounds or salts thereof which, according to the structural formula provided, may be assigned to the class of hydrazone derivatives and may be regarded as selected hydrazone peroxides. According to the teaching of the first of these two documents, they are prepared by reaction of .alpha.-halogen-azo compounds with sodium peroxide or hydrogen peroxide in the presence of acid acceptors and are then said to be used as polymerization initiators. Most of the Examples of this document and of the parallel, second US document mentioned describe the production of the hydroperoxide compounds by a method which is not explained in detail in the general disclosure of the invention. The selected hydrazone compounds in solution in a solvent are treated with a stream of oxygen by passing the oxygen through the solution of the hydrazone compounds kept at room temperature or at slightly elevated temperatures. The particular hydroperoxides are obtained in high yields of 80% or more and are optionally purified by low-temperature crystallization. The hydroperoxides may be used as starter systems for the polymerization of, for example, vinyl chloride or unsaturated polyester styrene resins.
A number of earlier publications are concerned with compounds of this type and their formation, particularly by autoxidation. As long ago as 1914, M. Busch et al. described the autoxidation of hydrazones in Ber. 47 (1914), 3277 to 3291. The alleged formation of the peroxides is postulated here as the addition of 1 molecule of oxygen onto the C:N double bond of the hydrazone with formation of a four-membered peroxide ring. The autoxidation of phenyl hydrazones is described again in K. H. Pausacker, J. Chem. Soc. 1950, 3478 to 3481. This publication reports on the non-catalyzed reaction of pure phenyl hydrazones and the corresponding reactions in the presence of a small quantity of benzoyl peroxide as catalyzed reactions. Further structural elucidation of the constitution of hydrazone peroxides is provided by R. Criegee et al. in Ber. 84 (1951), 219 to 224. It is shown here that the hydrazone peroxides can only be formed--at least at room temperature or correspondingly low temperatures--from derivatives of hydrazine compounds which contain a hydrogen atom at the substituted nitrogen atom.
The problem addresed by the present invention was to develop on the basis of existing knowledge new possibilities for the practical application of starters or activators and activator systems of the type in question which could be used in a simplified manner to initiate the polymerization of olefinically unsaturated systems. In admixture with radical-polymerizable substances or mixtures of the type used in practice, the activators would be inherently capable of activation by contact with ambient air. In preferred embodiments, this activation would actually take place at room temperature, although provision would be made for an increase in temperature where necessary. A particularly important aspect of the invention concerns multicomponent mixtures of the type mentioned which would be capable, simply by contact with ambient air at room temperature, of initiating the starting reaction of a radical polymerization of unsaturated systems with time-controlled curing and a predetermined pot life. In one important embodiment, the invention seeks in particular to provide one-component storable systems which would be moldable, more particularly paste-like to free-flowing, in their application form and which would have a sufficiently long pot life for processing, but would then cure in dimensionally stable form by simple exposure to ambient air.